So Vile a Sin is the fifty-sixth Virgin New Adventures novel in the series. However, due to writing and completion difficulties it was the last novel in the series featuring the Doctor to be published in May1997. It is also the last novel in the series to feature Roz Forrester, depicting her death on a battlefield.

The Great Houses of the Empire manoeuvre and scheme for advantage; alliances are made; and knives flash in the shadows. Out among the moons of Jupiter, another battle is just beginning, as an ancient brotherhood seeks limitless power and long-overdue revenge.

The Doctor returns to the thirtieth century, searching for the source of a terrifying weapon. He fears a nightmare from his own past may be about to destroy the future. Nothing must be allowed to get in his way.

But the Doctor has reckoned without the power of history - which has its own plans for the wayward daughter of the House of Forrester.

So Vile A Sin was to be written by Ben Aaronovitch. Due to various problems, Kate Orman assisted him in finishing it. However, it was still published late. The exact nature of the author's difficulties have never been fully clarified, with a hard drive failure and/or chronic writer's block being the two most widely reported at the time. As a result, although it occurs earlier in the continuity of the NA adventures, it was actually the last of the series to be published, being released after the NA's only Eighth Doctor novel, The Dying Days. This led to an unavoidable plot jump for readers, who went from PROSE: Damaged Goods to Bad Therapy only to discover the absence of Roz; they had to wait until the delayed publication of So Vile a Sin to find out what happened.

According to the acknowledgements on page 313 of So Vile A Sin: "Kate here. After Ben's troubles in writing So Vile A Sin, including a disastrous hard-drive crash, I stepped in at the last minute to finish it. Some of the book survived the crash, other bits existed as printouts, and Ben provided me with extensive plot and background notes to complete the bulk of the story."